No electrical power to dash or turn signals on a diesel 1982 International 584.

Hi; have a 1982 diesel International 584.

She starts and runs. Front lights work. Fuel gauge, revs and speed work. Hazards, indicators, horn, trailer power and cab components do not. A mystery to me without a multimeter (will buy this afternoon, but still don't understand 100%).
Using a 12v light tester I have power through the fuse's and good ground at the main battery to frame stud and at a rear cab bolt.
I haven't found any relays yet but suspect one of those or have heard of the ignition starving the power. Any ideas gratefully received.

Re: No electrical power to dash or turn signals on a diesel 1982 International 584.

#3 in the exploded view below, shows it to be a 35 amp automotive type fuse. The description says it powers most of the items you say do not work... At least a place to start with wiring etc, if the fuse is good.